Question 49

In the precipitation of the iron group (III) in qualitative analysis, ammonium chloride is added before adding ammonium hydroxide to:

Solution

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In Group III qualitative analysis, NH₄Cl is added before NH₄OH to suppress the ionization of NH₄OH (common ion effect). This decreases the OH⁻ concentration, ensuring only Group III hydroxides (which have lower Ksp) precipitate, while Group IV and V cations remain in solution.

The correct answer is Option 4: decrease concentration of OH⁻ ions.

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